Methods for synthesizing phosphonic compounds and compounds thereof

ABSTRACT

Described herein are methods for producing phosphonic compounds and compounds thereof.

IN THE CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/886,406, filed Jul. 7, 2004, which is hereby incorporated herein byreference in its entirety for all purposes.

BACKGROUND

Polyphosphonic acids have numerous applications in industry. Forexample, polyphosphonic acids can be used as corrosion inhibition agentsin cooling water and boiler water systems (U.S. Pat. Nos. 4,446,046 and4,201,669) and inhibitors of fouling deposit formation on jet enginecomponents during the combustion of finished turbine combustion fueloils (U.S. Pat. No. 5,596,130). One approach to the synthesis ofpolyphosphonic acids involves the radical polymerization of unsaturatedphosphonic acid monomers (U.S. Pat. Nos. 4,201,669, 4,446,046 and5,519,102).

An unsaturated phosphonic acid monomer that has received considerableattention is isopropenylphosphonic acid, which has the formulaH₂C═C(CH₃)(PO₃H₂), which is referred to herein as “IPPA.” IPPA iscurrently prepared by reacting PCl₃ with acetic acid and acetone (U.S.Pat. No. 4,446,046). This process, however, possesses numerousdisadvantages. First, PCl₃ is an extremely corrosive, hazardous, andtoxic chemical. It requires special handling starting fromtransportation to storage to delivery to reactors. Any release of PCl₃would require immediate evacuation. Second, the process produces HCl andacetyl chloride, which are also very hazardous and volatile by-products.The process is further complicated since these by-products come out as amixture and have to be scrubbed by water. This dilution magnifies thequantity of these by-products and leaves a mixture of HCl and acetylchloride in water. Finally, PCl₃ and the reaction by-products are verycorrosive and require special equipment such as glass-lined reactors,condensers, scrubbers, collection tanks, etc. The use of PCl₃ requiresthe use of equipment that is non-reactive with chlorides. Thus,equipment composed of other materials such as stainless steel cannot beused in the production of IPPA, which reduces large-scale commercialproduction capabilities.

Thus, it is desirable to have a process that produces phosphoniccompounds that are precursors to polyphosphonic compounds on large scalethat do not require the use of PCl₃ and/or specialized equipment such asglass-lined reactors and accessories, etc. It would also be advantageousnot to produce toxic, corrosive, and hazardous by-products during thesynthesis of the phosphonic compound. Finally, it would be desirable toproduce phosphonic compounds on commercial scale without specialequipment such as glass-lined reactors. The methods described hereinaccomplish these goals.

SUMMARY

Described herein are methods for producing phosphonic compounds andcompounds thereof.

The advantages of the invention will be set forth in part in thedescription which follows, and in part will be obvious from thedescription, or may be learned by practice of the aspects describedbelow. The advantages described below will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims. It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory only and are not restrictive.

DETAILED DESCRIPTION

Before the present compounds, compositions, articles, devices, and/ormethods are disclosed and described, it is to be understood that theaspects described below are not limited to specific compounds, syntheticmethods, or uses as such may, of course, vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular aspects only and is not intended to be limiting.

In this specification and in the claims that follow, reference will bemade to a number of terms that shall be defined to have the followingmeanings:

It must be noted that, as used in the specification and the appendedclaims, the singular forms “a,” “an” and “the” include plural referentsunless the context clearly dictates otherwise. Thus, for example,reference to “a pharmaceutical carrier” includes mixtures of two or moresuch carriers, and the like.

“Optional” or “optionally” means that the subsequently described eventor circumstance can or cannot occur, and that the description includesinstances where the event or circumstance occurs and instances where itdoes not. For example, the phrase “optionally substituted lower alkyl”means that the lower alkyl group can or can not be substituted and thatthe description includes both unsubstituted lower alkyl and lower alkylwhere there is substitution.

Ranges may be expressed herein as from “about” one particular value,and/or to “about” another particular value. When such a range isexpressed, another aspect includes from the one particular value and/orto the other particular value. Similarly, when values are expressed asapproximations, by use of the antecedent “about,” it will be understoodthat the particular value forms another aspect. It will be furtherunderstood that the endpoints of each of the ranges are significant bothin relation to the other endpoint, and independently of the otherendpoint.

References in the specification and concluding claims to parts byweight, of a particular element or component in a composition orarticle, denotes the weight relationship between the element orcomponent and any other elements or components in the composition orarticle for which a part by weight is expressed. Thus, in a compoundcontaining 2 parts by weight of component X and 5 parts by weightcomponent Y, X and Y are present at a weight ratio of 2:5, and arepresent in such ratio regardless of whether additional components arecontained in the compound.

A weight percent of a component, unless specifically stated to thecontrary, is based on the total weight of the formulation or compositionin which the component is included.

Variables such as R¹-R⁹ used throughout the application are the samevariables as previously defined unless stated to the contrary.

The term “alkyl group” as used herein is a branched- or straight-chainsaturated hydrocarbon group of 1 to 25 carbon atoms, such as methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, hexyl,heptyl, octyl, decyl, tetradecyl, hexadecyl, eicosyl, tetracosyl and thelike. A “lower alkyl” group is an alkyl group containing from one to sixcarbon atoms.

The term “cycloalkyl group” as used herein is a non-aromaticcarbon-based ring composed of at least three carbon atoms. Examples ofcycloalkyl groups include, but are not limited to, cyclopropyl,cyclobutyl, cyclopentyl, cyclohexyl, etc. The term “heterocycloalkylgroup” is a cycloalkyl group as defined above where at least one of thecarbon atoms of the ring is substituted with a heteroatom such as, butnot limited to, nitrogen, oxygen, sulphur, or phosphorus.

The term “aryl group” as used herein is any carbon-based aromatic groupincluding, but not limited to, benzene, naphthalene, etc. The term“aromatic” also includes “heteroaryl group,” which is defined as anaromatic group that has at least one heteroatom incorporated within thering of the aromatic group. Examples of heteroatoms include, but are notlimited to, nitrogen, oxygen, sulfur, and phosphonis. The aryl group canbe substituted or unsubstituted. The aryl group can be substituted withone or more groups including, but not limited to, allyl, alkynyl,alkenyl, aryl, halide, nitro, amino, ester, ketone, aldehyde, hydroxy,carboxylic acid, alkoxy, or SO₂R or S(O)₂OR, where R can be hydrogen oran alkyl group described above. The aryl group also includes aralkylsuch as, for example, benzyl. The aryl group of the aralkyl group can besubstituted with one or more groups listed above.

The term “protecting group” as used herein is a group that can bechemically bound to an oxygen atom, and subsequently removed (eitherchemically, in-vitro, or in-vivo) from the oxygen atom by predictablemethods. Examples of many of the possible protective groups can be foundin Protective Groups in Organic Synthesis by T. W. Green, John Wiley andSons, 1981, which is incorporated herein by reference in its entirety.

Disclosed are compounds, compositions, and components that can be usedfor, can be used in conjunction with, can be used in preparation for, orare products of the disclosed methods and compositions. These and othermaterials are disclosed herein, and it is understood that whencombinations, subsets, interactions, groups, etc. of these materials aredisclosed that while specific reference of each various individual andcollective combinations and permutation of these compounds may not beexplicitly disclosed, each is specifically contemplated and describedherein. Thus, if a class of molecules A, B, and C are disclosed as wellas a class of molecules D, E, and F and an example of a combinationmolecule, A-D is disclosed, then even if each is not individuallyrecited, each is individually and collectively contemplated. Thus, inthis example, each of the combinations A-E, A-F, B-D, B-E, B-F, C-D,C-E, and C-F are specifically contemplated and should be considereddisclosed from disclosure of A, B, and C; D, E, and F; and the examplecombination A-D. Likewise, any subset or combination of these is alsospecifically contemplated and disclosed. Thus, for example, thesub-group of A-E, B-F, and C-E are specifically contemplated and shouldbe considered disclosed from disclosure of A, B, and C; D, E, and F; andthe example combination A-D. This concept applies to all aspects of thisdisclosure including, but not limited to, steps in methods of making andusing the disclosed compositions. Thus, if there are a variety ofadditional steps that can be performed it is understood that each ofthese additional steps can be performed with any specific embodiment orcombination of embodiments of the disclosed methods, and that each suchcombination is specifically contemplated and should be considereddisclosed.

Described herein are methods for producing phosphonic compounds. In oneaspect, a method for making the phosphonic compound involves reactingcompounds I, II, and III

wherein R¹-R⁷ can be, independently, hydrogen, an alkyl group, acycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroarylgroup, a protecting group, or a combination thereof.

The selection of compounds I, II, and III will vary depending uponreaction conditions and the desired phosphonic compound to be produced.In one aspect, with respect to compound I, R¹ and R⁷ can be,independently, hydrogen, an alkyl group, a cycloalkyl group, aheterocycloalkyl group, an aryl group, a heteroaryl group, a protectinggroup, or a combination thereof. In another aspect, R¹ and R⁷ in formulaI are hydrogen. This compound (H₃PO₃) is referred to as phosphorous acidor phosphonic acid, which is a stable powder and much easier to handlewhen compared to PCl₃. Indeed, phosphonic acid is more environmentallyfriendly and substantially more stable than PCl₃, and can be transportedin bags to storage or to the reactor. In a further aspect, R¹ and R⁷ canbe, independently, methyl, ethyl, propyl, isopropyl, butyl, pentyl, orhexyl. In the case when R¹ and R⁷ are methyl, the compound is dimethylhydrogen phosphite. In another aspect, R¹ and R⁷ can be aryl groups suchas phenyl or cycloalkyl groups.

In one aspect, R²-R⁴ of formula II can be, independently, hydrogen, analkyl group, a cycloalkyl group, a heterocycloalkyl group, an arylgroup, a heteroaryl group, a protecting group, or a combination thereof.In one aspect, R² and R³ in formula II is hydrogen. In another aspect,R² and R³ in formula II are hydrogen and R⁴ can be a branched- orstraight-chain alkyl group such as, for example, methyl, ethyl, propyl,isopropyl, butyl, pentyl, or hexyl. In another aspect, R² and R³ informula II are hydrogen and R⁴ can be an aryl group or a heteroarylgroup such as, for example, a phenyl group. In another aspect, compoundII can be acetone, methylphenyl ketone (R² and R³ are hydrogen, R⁴ isphenyl), sulfonated benzyl methyl ketone (R² and R³ are hydrogen, R₄ isCH₂—C₆H₄-p-SO₂OH), or ethanal (R², R³, and R⁴ are hydrogen).

In one aspect, R⁵ and R⁶ of formula III can be, independently, hydrogen,an alkyl group, a cycloalkyl group, a heterocycloalkyl group, an arylgroup, a heteroaryl group, a protecting group, or a combination thereof.In one aspect, R⁵ and R⁶ can be, independently, a branched- orstraight-chain alkyl group such as, for example, methyl, ethyl, propyl,isopropyl, butyl, pentyl, or hexyl. In another aspect, formula III canbe acetic anhydride, propionic anhydride, or butyric anhydride.

The reaction for producing the phosphonic compound can optionally beperformed in the presence of a catalyst. In one aspect, the catalyst canfacilitate the formation of the phosphonic compound. In another aspect,a compound having the formula R⁸COOH, wherein R⁸ can be C₁-C₈ branched-or straight-chain alkyl such as, for example, methyl, ethyl, propyl,isopropyl, butyl, pentyl, or hexyl can be used as the catalyst. Notwishing to be bound by theory, it is believed that the catalyst cansolubilize one or more intermediates that ultimately lead to theproduction of the phosphonic compound. The catalyst can be added to thereaction as a separate component or can be produced in situ. Forexample, when compound I is phosphorous acid, compound II is acetone,and compound III is acetic anhydride, glacial acetic acid is producedduring the reaction. In this example, the glacial acetic acid can beisolated and sold commercially or used in future reactions.

The amount of components I, II, and III can vary depending upon thecompounds selected and reaction conditions. In one aspect, the amount ofcomponent I is from 10% to 25%, 15% to 25%, or 15% to 20% by weight, theamount of component II is from 10% to 25%, 15% to 25%, or 15% to 20% byweight, and the amount of component III is from 10 to 70%, 20% to 60%,or 30% to 60%, by weight, wherein the sum of components I-III is 100%.When a catalyst is used, in one aspect, the amount of catalyst is from1% to 50%, 5% to 40%, 5% to 30%, or 5% to 25% by weight, wherein the sumof components I-III and the catalyst is 100%. Components I-IIII and theoptional catalyst can be added to one another in any order using themethods described herein. This is not the case when PCl₃ is used as thestarting material. For example, in U.S. Pat. No. 4,446,046 (the '046patent), the addition of acetic acid to PCl₃ is very dangerous and canbe explosive if performed on a large scale. The methods described hereindo not use PCl₃ and, thus, this is not an issue. In one aspect,components I, III, and the catalyst are mixed with one another followedby the addition of component II.

The reaction time and temperature can vary as well depending upon theselection of components I-III. In one aspect, the reaction temperaturecan range from 10° C. to 200° C., 10° C. to 190° C., 10° C. to 180° C.,15° C. to 180° C., 15° C. to 170° C., 15° C. to 160° C., or 15° C. to150° C. Reaction temperatures can fluctuate during the reactiondepending upon the selection of components I-III. In one aspect, therate of addition of component II can vary in order to control thetemperature of the reaction.

In one aspect, the reaction time can be from 3 minutes to 10 hours, 10minutes to 8 hours, 10 minutes to 6 hours, 10 minutes to 4 hours, 10minutes to 2 hours, 10 minutes to 1 hour, or 30 minutes to 1 hour. Thereaction times using the methods described herein are generally muchlower than processes that use PCl₃. For example, IPPA can be producedfrom phosphorous acid, acetone, and acetic anhydride with acetic acid asthe catalyst in approximately 5 hours. Conversely, if IPPA is producedfrom PCl₃ using the process in the '046 patent, the reaction can takefrom 25 to 44 hours. One reason why the process in the '046 patent issubstantially longer than those described herein is that this processproduces HCl and acetyl chloride, which are very toxic and have to beremoved by vacuum. HCl and acetyl chloride are the two by-products thatare produced when PCl₃ is used. As long as PCl₃ is being added, theseby-products will continue to come out of the reactor and need to bequickly removed under atmospheric pressure or under vacuum. This canjeopardize the reaction, because the starting materials could bevolatile and removed from the reaction when the by-products are removed.This is not the case with the present invention, where HCl and acetylchloride are not produced.

The methods described herein can be performed using readily availableequipment and do not require special equipment or handling as requiredin the process disclosed in the '046 patent. For example, the processdisclosed in the '046 patent requires glass-lined reactors, specialcollection tanks, and scrubbing systems to capture the HCl and acetylchloride. The methods described herein permit the use of equipment suchas, for example, stainless steel reactors, and normal collection tanksand condensers, which are widely available, much less expensive, andeasier to operate and maintain. Thus, the methods described hereinpermit the large-scale production of phosphonic compounds in acommercially practical way.

In one aspect, the phosphonic compounds produced by the methodsdescribed have the formula IV

wherein R¹-R⁴ and R⁷ can be, independently, hydrogen, an alkyl group, acycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroarylgroup, a protecting group, or a combination thereof. In one aspect, R⁴in formula IV is not an alkyl group. The compounds represented informula IV are referred to herein as unsaturated phosphonic compounds.In one aspect, R² and R³ in formula IV can be hydrogen. In anotheraspect, R⁴ in formula IV can be an aryl group or a heteroaryl group. Inanother aspect, R¹ and R⁷ in formula IV can be hydrogen. In anotheraspect, the compound having the formula IV has the formulaH₂C═C(R⁹)(PO₃H₂), where R⁹ can be hydrogen, substituted or unsubstitutedphenyl, or substituted or unsubstituted benzyl (e.g.,CH₂C₆H₄-p-S(O)₂OH).

In one aspect, the phosphoric compounds produced by the methodsdescribed have the formula VII

wherein R¹-R⁴ can be, independently, hydrogen, an alkyl group, acycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroarylgroup, a protecting group, or a combination thereof. The compoundsrepresented in formula VII are dimers of the compounds having theformula IV. In one aspect, R² and R³ in formula VII can be hydrogen. Inanother aspect, R⁴ in formula VII can be an aryl group or a heteroarylgroup. In another aspect, R¹ in formula VII can be hydrogen.

In another aspect, the phosphonic compounds produced by the methodsdescribed herein have the formula V

wherein R¹-R⁵ and R⁷ can be, independently, hydrogen, an alkyl group, acycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroarylgroup, a protecting group, or a combination thereof. In another aspect,the phosphonic compounds produced by the methods described herein havethe formula VI

wherein R¹-R⁵ and R⁷ can be, independently hydrogen, an alkyl group, acycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroarylgroup, a protecting group, or a combination thereof.

Compounds having the formula V and VI are precursors to the unsaturatedphosphonic compounds IV and VII, respectively. For example, compound IVis produced if R⁵C(O)OH is eliminated from compound V. Similarly,compound VII is produced from compound VI with the loss of twoequivalents of R⁵C(O)OH. Compound VI is the dimer of compound V.Depending upon reaction conditions, the selection of components I-III,and the use of a catalyst, it is possible to produce compounds IV-VIIindividually or as mixtures of compounds. For example, if excess aceticanhydride (compound III) is used in the reaction, that can promoteformation of compound VI.

Any of the unsaturated phosphonic compounds produced herein (compoundsIV and VII) can be polymerized using techniques known in the art. Forexample, the techniques disclosed in the '046 patent, which isincorporated by reference for its teachings as it relates topolymerization chemistry, can be used herein to polymerize compoundshaving the formula IV and VII.

EXAMPLES

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how thecompounds, compositions, and methods described and claimed herein aremade and evaluated, and are intended to be purely exemplary and are notintended to limit the scope of what the inventors regard as theirinvention. Efforts have been made to ensure accuracy with respect tonumbers (e.g., amounts, temperature, etc.) but some errors anddeviations should be accounted for. Unless indicated otherwise, partsare parts by weight, temperature is in °C. or is at ambient temperature,and pressure is at or near atmospheric. There are numerous variationsand combinations of reaction conditions, e.g., component concentrations,desired solvents, solvent mixtures, temperatures, pressures and otherreaction ranges and conditions that can be used to optimize the productpurity and yield obtained from the described process. Only reasonableand routine experimentation will be required to optimize such processconditions.

Example 1 Preparation of Isopropenylphosphonic Acid (IPPA)

To a 1.0 L, 3-necked flask equipped with a magnetic stirring bar and anaddition funnel, was added 164 g (2.0 moles) of dry, anhydrousphosphorus acid. Acetic anhydride (400 g; 3.9 moles) was added followedby acetic acid (160g; 2.6 moles). The addition funnel was removed, andthe flask was then equipped with a heating mantel, magnetic stirrer,thermometer, reflux condenser, and pressure compensated addition funnel.The mixture was stirred at ambient (19° C.) temperature until a clearsolution was obtained (10 min; 18° C.). Acetone (140 g; 2.4 moles) wasadded dropwise through the addition funnel. The temperature started torise steadily after 3 min of acetone addition and by the time 35 g (0.6moles after 12 min.) of acetone was added, the temperature had risenfrom 18° C. to 23° C. The temperature steadily rose to 40° C. by thetime 105 g (1.8 moles at 32 min.) of acetone was added. Acetone additionwas stopped, and the mixture was allowed to cool for 8 minutes. Acetoneaddition was resumed at 37° C., and it took 10 minutes to add the restof the acetone 35 g (0.6 moles). The temperature climbed to 52° C. thencompletely stopped. Thus, it took 50 minutes to add all the acetone.Optionally, a balance of constant cooling and constant adding of acetonecan be maintained. During acetone addition, no acetone was seenrefluxing, which indicated that an immediate and stable reactionoccurred. Also, the temperature only rose with each further addition ofacetone and, the temperature did not rise when acetone addition stopped.The reaction showed extreme control and can be stopped at any point, ifnecessary. In addition, white oligomers (formula V and VI) were seentemporarily The above mixture was allowed to stir at 50 to 60° C. (lowheat was occasionally applied to maintain temperature) for one hour.Moderate heat was then applied, and the temperature was allowed tosteadily rise to 100° C.

At this point, a reflux condenser was replaced by an adapter, athermometer, and a horizontal reflux condenser that was connected to acollection flask that was connected to a trap en route to a vacuum pump.When temperature reached 118° C., distillate was allowed to collect inthe flask while the temperature continued to rise to 140° C. Vacuum wasthen gradually applied (to prevent surge of distillate) until fullvacuum was obtained. At 170° C. and full vacuum, no more distillate wasproduced, with a total distillate collected at 623 g (99%). This clear,colorless distillate was confirmed to be 100% pure acetic acid.

During the whole process (ca., 4½ hrs. between the addition ofreactants, hold period, heating and collecting), the product mix wascolorless until about 80° C. when the product turned straw-colored. At90° C., it turned light yellow and at 110° C., it looked yellow-orange(amber), while at 140° C. it was dark amber. The final product IPPA(residue) at 170° C. was a viscous, golden-yellow liquid and weighed 234g.

P³¹ NMR showed two main peaks: one single peak at delta 20.8 PPM (29%)and one single peak at delta 10.2 PPM (71%). These peaks correspond toisopropenyl phosphonic acid monomer (IPPA) (C₃H₇O₃P, 29%) andisopropenyl phosphonic acid anhydride dimer (IPPAA) (C₆H₁₂O₅P₂, 71%).

Example 2 Large-Scale Production of Isopropenylphosphonic Acid (IPPA)

Table 1 shows the amount of starting materials used to produce IPPA onlarge scale using PCl₃ as described in Example 3 of the '046 patentwhile Table 2 shows the amount of by-products that would be producedfrom this process. Table 3 shows the amounts of starting materials usedto produce IPPA using the methods described herein. Table 4 indicatesthat the only by-product is glacial acetic acid, which can be recoveredas 100% pure acetic acid and sold in the open market.

TABLE 1 Raw Materials Pounds Mol. Wt Moles B.P. ° C. Gallons Acetone1320 58.08 22.73 56.5 200 Acetic Acid-Glacial 6358 60.05 105.87 118 735PCl₃ 3212 137.3 23.39 76 243 Total 10890 152 1178

TABLE 2 Raw Materials Pounds Mol. Wt Moles B.P. ° C. GallonsHydrochloric Acid 1136 36.46 28.85 — 362 Acetyl Chloride 3060 78.5038.98 52 333 Acetic Acid 4019 60.05 28.86 118 465 Total 8215 66.92 1160

TABLE 3 Raw Materials Pounds Mol. Wt Moles B.P. ° C. Gallons PhosphorousAcid 1918 82 23.39 — — Acetic Anhydride 4674 102 45.83 139 514 AceticAcid 1871 60.05 31.16 118 216 Acetone 1638 58.08 28.21 56 248 Total10101 978

TABLE 4 Raw Materials Pounds Mol. Wt Moles B.P. ° C. Gallons Acetic Acid7136 60.05 118.8 118 825

The process used in the '046 patent produces 1,160 gallons of mixedhazardous materials (HCl and acetyl chloride in acetic acid and water)(Table 2). The acetyl chloride, HCl, and acetic acid cannot be separatedin actual production. Conversely, use of the process described hereinproduces only glacial acetic acid (Table 4, 825 gallons), which can berecovered and sold in the open market. If one million pounds of IPPAwere produced using the process in the '046 patent, theoretically406,000 gallons of HCl, acetyl chloride, and acetic acid would beproduced, which would create numerous environmental and safety issues.The use of the process described herein, however, theoretically produces289,000 gallons of glacial acetic acid, which can be recovered and soldin the open market.

Throughout this application, various publications are referenced. Thedisclosures of these publications in their entireties are herebyincorporated by reference into this application in order to more fullydescribe the compounds, compositions and methods described herein.

Various modifications and variations can be made to the compounds,compositions and methods described herein. Other aspects of thecompounds, compositions and methods described herein will be apparentfrom consideration of the specification and practice of the compounds,compositions and methods disclosed herein. It is intended that thespecification and examples be considered as exemplary.

1. A method for making a compound, comprising admixing togethercompounds I, II, and III

wherein R¹-R⁷ comprises, independently, hydrogen, an alkyl group, acycloalkyl group, a heterocycloalkyl group, an aryl group, a heteroarylgroup, a protecting group, or a combination thereof, wherein compoundsI, II and III react to produce a compound comprising the formula IV

wherein R¹-R⁴ and R⁷ comprises, independently, hydrogen, an alkyl group,a cycloalkyl group, a heterocycloalkyl group, an aryl group, aheteroaryl group, a protecting group, or a combination thereof.
 2. Themethod of claim 1, wherein R¹ and R⁷ are hydrogen.
 3. The method ofclaim 1, wherein R¹ and R⁷ comprises, independently, methyl, ethyl,propyl, isopropyl, butyl, pentyl, or hexyl.
 4. The method of claim 1,wherein R¹ and R⁷ are methyl.
 5. The method of claim 1, wherein R² ishydrogen and R⁴ comprises a branched or straight chain alkyl group. 6.The method of claim 1, wherein R² and R³ are hydrogen.
 7. The method ofclaim 1, wherein R², R³, and R⁴ are hydrogen.
 8. The method of claim 6,wherein R⁴ comprises a branched- or straight-chain alkyl group.
 9. Themethod of claim 8, wherein R⁴ comprises ethyl, propyl, isopropyl, butyl,pentyl, or hexyl.
 10. The method of claim 8, wherein R⁴ comprisesmethyl.
 11. The method of claim 6, wherein R⁴ comprises an aryl group ora heteroaryl group.
 12. The method of claim 6, wherein R⁴ comprises aphenyl group.
 13. The method of claim 1, wherein compound II comprisesethanal, methylphenyl ketone, or sulfonated benzyl methyl ketone. 14.The method of claim 1, wherein compound II comprises acetone.
 15. Themethod of claim 1, wherein R⁵ and R⁶ comprises a branched- orstraight-chain alkyl group.
 16. The method of claim 1, wherein R⁵ and R⁶comprises, independently, methyl, ethyl, propyl, isopropyl, butyl,pentyl, or hexyl.
 17. The method of claim 1, wherein compound IIIcomprises acetic anhydride, propionic anhydride, or butyric anhydride.18. The method of claim 1, wherein compound I comprises phosphorousacid, compound II comprises acetone, and compound III comprises aceticanhydride.
 19. The method of claim 1, wherein the reaction is conductedin the presence of an optional catalyst.
 20. The method of claim 19,wherein the catalyst comprises R⁸COOH, wherein R⁸ comprises C₁-C₈branched- or straight-chain alkyl.
 21. The method of claim 20, whereinR⁸ comprises methyl, ethyl, propyl, isopropyl, butyl, pentyl, or hexyl.22. The method of claim 19, wherein the catalyst comprises acetic acid.